THE EFFECT OF AN IRON DRUG ON HOST RESPONSE TO EXPERIMENTAL PLAGUE INFECTION

The effect of iron administration on experimental plague infection was studied with colloidal iron chondroitin sulfate. The mice inoculated subcutaneously with an attenuated plague strain took the fatal outcome when they were treated with the drug; the resulted histopathological changes were similar to those of the animals infected with a virulent strain. An early appearance of clumped bacilli, parenchymal cell infiltration, granuloma and necrosis in the liver, and atrophy of red pulp, hyperplasia or necrosis or both of follicles in the spleen and lymph nodes were the main findings in the iron-administered mice. In contrast to these, the iron-untreated mice showed only perivascular lesions in the liver and slight changes in the spleen. The drug administration suppressed the development of immunity in mice in response to a protective antigen, Fraction I. Additional experiments demonstrated that the drug has no toxicity-increasing effect on the murine toxin. From these observations, the “virulence-enhancing” effect of iron can be explained as an interfering with the host defense mechanism.